Genomic analysis of the citrate metabolism in Enterococcus faecium strains

SUAREZ, CRISTIAN; QUINTANA, INGRID; MORTERA, PABLO; EBERHARDT, FLORENCIA; MAGNI, CHRISTIAN

Foz de Iguazú

Congreso; XVI World Congress of Food Science and Technology; 2012

Asociación Latinoamericana y del Caribe de Ciencia y Tecnología de Alimentos – ALACCTA

Citrate metabolism is widespread among lactic acid bacteria (LAB). The ability to metabolize citrate is dependent on the presence of different citrate transporters which allow the specific uptake. Although in all case, the citrate lyase complex which split citrate into oxaloacetate and acetate are essential to the citrate utilization by LAB. Enterococcus faecium is present in commercial and artisanal dairy products (cheeses) and contribute to the organoleptic feature. The capacity to ferment citrate by E. faecium was previously studies. However little is known about the genetic organization of the genes involved in the citrate utilization (cit clusters). Our comparative genomic analysis reveals one population of E. faecium (type I) where the cit cluster is absent. In the E. faecium type II the cit clusters are composed by citrate transporter (CitHM family), the transcriptional activator citO and citrate lyase complex (citDEF) associated to membrane oxaloacetate decarboxylase genes (oadHABD). Finally, in the last type of E faecium (type III) the transcriptional activator CitI is divergent located to soluble oxaloacetate decarboxylase (citM), citrate transporter (2HCT family) and genes codifying the citrate lyase complex (citDEF). To start our molecular characterization, twenty E. faecium strains isolated from commercial and artisanal cheese were analyzed for the ability to used citrate. Both type of phenotype (Cit+ or Cit-) were indentified in our isolated. We could identify by PCR E. faecium belonging to the types I and III and physiological studies were performed in these strains.